This invention relates to a compact, modular, constant current DC arc welding apparatus of the consumable electrode type (DC Stick and/or MIG) which is also capable of providing welding current for a non-consumable welding process (TIG) which is designed to be attached to, and to be directly or indirectly driven by, any suitable drive motor. Suitable drive motors include, but are not limited to, internal combustion engines, hydraulic motors, pneumatic motors, and electric motors. The modular welding apparatus of this invention generates welding current by means of a specially constructed high-current alternator, hereinafter referred to as a welding power generator, an electronic power control apparatus, and a remote operator control apparatus.
This invention produces a DC welding current with a pulsating high-frequency ripple component, hereafter referred to as high frequency DC welding current, which provides a number of improved technical welding characteristics. For example, this high frequency DC welding current can be transmitted over relatively long distances when compared to a pure DC current, with much less power loss due to the resistive and inductive effects of transmission cables, reducing the usual need to increase welding cable cross sectional size when using longer welding cables. This high frequency DC welding current also enables a weldor to produce very high quality welds, which show greater penetration into the workpiece for a given power setting when compared with prior art. The high frequency DC welding current also produces an exceptionally easy to start and easy to maintain welding arc which can be used successfully, without weld degradation, over a very wide range of arc to weld puddle lengths, including use with the electrode placed in direct contact with, or within, the weld puddle itself. Because of its ability to maintain a suitable welding arc with the electrode placed within a weld puddle, completely isolated from atmospheric and other external impurities, the high frequency DC welding current generated by the invention produces weld joints with less internal defects.
This invention""s electronic power control apparatus works in conjunction with the invention""s power generating apparatus to generate a very precisely controlled welding current output without the need for either precise control of drive motor speed, or a complicated electrical or mechanical power control system which relies on output power sensing or any sort of electrical or mechanical feedback. The invention""s electronic power control apparatus also provides a means to control the electrical and operational characteristics of the aforementioned high frequency DC welding current.
The invention also incorporates a complete set of welder operation controls (i.e., power on/off, output amperage, arc starting, momentary power boost) which are integrated ergonomically into the invention""s electrode holder, eliminating the need for a weldor/operator to leave a work location to make any adjustments to the welding power generating apparatus. A safety interlock is also included in the invention""s control apparatus to provide additional weldor/operator safety.
The modular design of the invention""s power generating apparatus and its electronic power control apparatus allow a plurality of individually operated, and independently controlled, compact, modular, constant current DC arc welding apparatuses to be attached to, and powered by, a single drive motor without any undesirable interaction between the individual components.
Further, the invention""s compact, modular, welding power generator and its electronic power control apparatus also make it possible for a plurality of separate welding power generators to be attached to, and driven by, a single drive motor, with their welding current outputs connected in parallel, and with all of the interconnected welding power generators controlled by a single electronic power control apparatus without any undesirable interaction between the individual components. Thereby providing a means to generate, and to precisely control, very high welding currents (i.e., from 300 to over 800 amps.) with a very high degree of efficiency, and at a very low manufacturing cost, when compared with any prior art. For example, conventional motor-driven high-amperage welders must be very massively constructed to operate reliably and to provide a means to dissipate high internal heat generated while producing large welding currents. It is easy to see, therefore, the great advantage provided by the modular aspects of this invention, when compared to prior art.
This invention, because of its compact size and modular construction, is also universally retrofittable into any motor driven vehicle (i.e., tractors, automobiles, trucks, construction equipment, mowing equipment, nursery equipment, mining equipment, logging equipment, military equipment, all-terrain vehicles, amphibious vehicles, and water-craft), thereby creating a new class of welding equipment.
Electric arc welding requires a relatively high power current source. In the case of mobile and/or portable welders, this power source typically consists of a motor driving a DC generator or an alternator. Given the high weight, and expense of DC generators, most modern motor driven welding devices utilize an alternator as the power source. This power source must generate sufficient AC or DC current to melt welding electrodes that range from {fraction (1/16)} to {fraction (5/16)} inch in diameter and are 9 to 18 inches in length. The power source must also be able to provide sufficient voltage to start, and to maintain, an electrical welding arc. Normally the arc welding power source has two terminals. One terminal is connected via a flexible cable to the work piece to be welded, and the other is connected via a second flexible cable to an electrode holder. The electrode holder is an insulated metal clamp supported by an insulated handle which is gripped by the equipment operator.
Particularly with DC welders, the size and length of the flexible electrical cable used to connect the arc welding source to the workpiece and to the electrode holder is of critical importance, requiring larger and larger cable sizes as the distance from the welder to the workpiece increases. As cable size and/or length increases, equipment cost increases, utility of the equipment decreases, and workload placed on weldors operating the equipment increases.
Consumable electrodes are typically used with electric arc welding equipment.
Approximately one inch at one end of the welding electrode is bare metal to insure good electrical contact when it is gripped by an electrode holder clamp. The remainder of the electrode is coated with various chemical formulations (fluxing agents, arc stabilizers, metal powders, and other substances). These coatings exhibit little insulating effect and when a weldor grips an electrode and places it into the jaws of the electrode holder, the weldor is at considerable risk of electrical shock. Since a welding electrode is consumed in about three minutes, many electrode changes may be required to complete a job. Each change of electrode provides a risk of electrical shock. As time passes, a weldor""s gloves to grow damp with perspiration, greatly decreasing any insulating effect that these gloves may provide. Weldors are, therefore, frequently shocked. On most occasions this shock is simply painful, but under the right circumstances, this shock may be fatal or disabling.
There have been a number of systems designed to better control a welding power source (as described, for example, in U.S. Pat. No. 4,216,368, and U.S. Pat. No. 5,864,117), but their technical deficiencies, and/or their high expense, have prevented their general acceptance and widespread use, particularly in lower-cost general purpose welding equipment. Further, none of these control systems have been particularly applicable to motor-driven welders designed to operate away from electrical utility supplied AC power. For example, in prior art, welding power control and/or welding power regulation systems most typically require some form of electrical and/or mechanical feedback to the control circuits and/or engine governing systems used by these devices to produce well regulated constant current and/or constant voltage welding output. Therefore, most welding, particularly welding which uses motor-driven alternators for a welding power source, is often done without having efficient, and/or accurate, and/or low cost control of the welding current transmitted to the electrode holder.
Another example of prior art, U.S. Pat. No. 2,658,132, describes a control system for a constant speed electric motor driven DC generator which used expensive saturable reactors, transformers, and relays to control DC generator output and which utilized relay control of the electric motor and a rotor control power supply transformer to switch power on and off. Yet, for all the complexity of this design, it fails to provide a constant welding current output or a proper open circuit voltage across a wide range of output currents and it provides no means to deal with the effects of motor speed variations should such occur (as would be common in most motor driven welders).
In the past, designs for low-cost motor driven, alternator powered welding systems have attempted to utilize modified or unmodified automotive type alternators (used with or without other supplementary external power sources). Frequently, prior art, in its attempts to successfully generate welding current with alternators, has required expensive custom alternator designs, and/or complex custom transformers, and/or other design features that have often limited welding capabilities, and/or made the welders built with this prior art expensive, and/or difficult to mass produce. For example:
1. Prior art (such as that described in U.S. Pat. No. 4,853,557) which relies on complex external power control and/or switching devices have been primarily limited to under-hood automotive applications where the components can be somewhat protected from adverse environmental conditions. Often designs of this type even further limit the use of such prior art only to completely protected (dry, in-door/under cover) environmental conditions.
2. Prior art (such as described in U.S. Pat. No. 4,330,715 and U.S. Pat. No. 5,734,147), has often required the incorporation of complex feedback and/or auxiliary power increasing schemes, and/or external battery supplies (such as described in U.S. Pat. No. 5,506,492) which are designed to produce better welds when operating the alternator at rotational speeds which are inefficient for generating proper welding currents, or to compensate for design limitations which are inherent in standard automotive alternators which are not typically designed to produce high power for extended periods of time.
3. Prior art (as described in U.S. Pat. No. 5,670,070) well illustrates the level of complexity previously required to successfully use alternators as welding power sources. In this example, direct adjustment and control of stator output is the proposed solution. However, to implement this control system, complicated switching and timing circuitry as well as rather extensive internal wiring is required to enable the use of six (6) SCR""s (Silicon Controlled Rectifiers) which replace standard alternator rectifiers, within a specially constructed alternator.
4. Prior art (as described in U.S. Pat. No. 3,593,121) has also required complicated multiple variable transformers or auto transformers mechanically linked to each other and to an electrical control means such as a potentiometer which are used in conjunction with a custom built alternator, with electrical performance and impedance characteristics matching those of the transformers or autotransformers noted previously, in order to achieve a stable alternator powered arc welding power source of the constant voltage type. However, it is ineffective for providing a constant current welding power supply of the type required for consumable electrode welding (i.e., DC stick or MIG).
5. Prior art frequently utilizes adjustment of the driving motor speed as a primary method of welder power control. When used without complicated and expensive speed governing equipment, a highly undesirable result of this type of control is to force a welder/operator to deal with dramatically differing welding characteristics caused by nonlinear and often large variations in output power caused by drive motor speed variations which occur under a widely varying load.
For example, going from no arc to a fully developed high current welding arc may place an extreme load on the drive motor and reduce welding output just when a stable or even an increased output is most critically required. This makes arc starting difficult even at higher amperages. However, when working with welding currents of less than 90 amps. alternator output voltages are typically too low, even if operating in a stable fashion, to achieve an easy to start and easy to maintain welding arc.
6. Prior art has also neglected to deal effectively with the excessive heat build-up in the alternator""s stator windings and core and the resulting potential for premature electrical failure that may occur whenever an alternator""s field is excited without an electrical load being placed on the alternator for extended periods of time, as occurs typically in devices based on prior art.
7. Prior art has been unable to efficiently and to properly utilize varying sizes of consumable welding electrodes without the use of relatively complicated electronic power and voltage regulating circuitry. Nor has it dealt with the need to reliably strike an arc to begin welding. Typically, alternator powered welding equipment does not generate sufficient voltage for arc generation except at higher engine speeds and higher (over 90 amperes) welding currents. For example, to weld with a smaller diameter electrode in a welder that relies on engine speed power control, engine speed would have to be very high to start an arc then drop almost instantly to a predetermined set speed for actual welding. U.S. Pat. No. 5,861,604 has offered a complicated, expensive, and relatively unreliable method of dealing with this problem in non-motor-driven welding equipment. But it is not readily applicable to alternator based motor-driven devices.
8. Prior vehicle engine driven alternator powered welding systems have required precise speed control to provide proper welding current output requiring either expensive engine speed governing devices or special operator-adjustable throttle controls to provide proper control of welding power. Because engine speed cannot change instantaneously, when using these types of controls, effective variation of welding power is not possible while welding, greatly limiting the ability of this type of welder to perform in commercial welding applications.
9. Prior vehicle engine driven alternator powered welding systems have required very large power generating apparatus with the physical size being determined by the output power required and by the need to dissipate significant amounts of internal heat within the body of the generating apparatus. For example, a power generating apparatus which would produce 300 amps. of continuous welding power would have to be approximately 2.5 times as large physically as a power generating unit capable of producing 150 amps of continuous welding power. In some cases, expensive liquid cooling systems have been utilized to control welding power generator waste heat.
In the past, alternator powered welding apparatus controls have been typically attached somewhere near, but external to, the power generating apparatus of the welding device. Typically these controls fall into two categories, engine speed controls and/or electronic controls that vary alternator operation. These controls are used to adjust the output power of the arc welder to meet the technical requirements of the job that is being attempted by the weldor and on/off control of the device itself.
For example, in order to successfully weld a material of a given thickness, the use of such alternator powered welding equipment requires the weldor/operator of the equipment to select output power via engine speed control to produce a proper weld when considering material thickness, ambient temperature, type of weld shielding (gas or chemical), thickness of electrode(s), condition of material being welded (clean or oxidized), and the expected or desired speed of weld bead deposit on the work piece. Frequently this welding power selection is accomplished through a trial and error process, particularly since precise control of engine speed is very difficult to accomplish in ungoverned vehicle engines. Since the work piece is often some distance from the power generating equipment, travel to and from the welding device is a time and effort wasting process. To solve this, some designs have utilized remotely adjustable engine speed control mechanisms that allow engine speed adjustment from a remote location. However, mechanical limitations constrain such remote controls to operation over relatively short distances (10-20 ft.). If longer welding cables are utilized and/or required, time wasting travel to and from the mechanical engine speed adjustment mechanism to the work site will still be required. Designs of the sort described in U.S. Pat. No. 4,216,367 have addressed this issue in the past.
On/off control of alternator powered welding equipment in prior art has also typically been accomplished at or near the power generating device. Since power is applied to the welding electrode when the device is switched on, extreme caution must be taken by the equipment operator to insure that the welding electrode is positioned and held in such a way as to insure that no inadvertent contract between the electrodes and a metal surface can occur while the weldor/operator is adjusting controls and preparing to weld. Further, since power is applied continuously to the welding electrode, when working in confined spaces, the weldor/operator must exercise extreme caution when positioning the welding electrode prior to beginning a weld. For example, should inadvertent contact with a metal surface occur an electrical arc can occur in such a way as to damage the weldor/operator""s eyesight. to cause an explosion, or to cause the weldor/operator to incur severe burns. Designs of the sort described in U.S. Pat. No. 4,151,396 have addressed this in the past with rather complex, and potentially unreliable electronic controls.
U.S. Pat. No. 2,658,132, describes a system of remote controls conveniently mounted within the electrode holder which is part of a welding system made up of an electrical control means, a large AC motor, and a DC generator. These controls provide a mechanism for controlling the DC generator""s output power and for turning said DC generator on and off. However, the effect of these controls on the DC generator is not immediate and, because of residual magnetism in the DC generator""s components which may still be rotating even after welding power is switched off, power sufficient to produce a dangerous arc may still be generated even though an operator believes the power to be switched off. This limitation makes these controls ineffective as a safety device. Further, motor startup delay in this design causes a corresponding delay in the production of usable welding power by the DC generator when an operator switches power on. This can produce unpredictable and potentially dangerous results when an operator is attempting to use the on/off control on the electrode holder as a safety device. Given the limitations noted, it is not surprising that claims relating to the use of the control means defined in this invention as either an operator safety mechanism, or as a means to prevent unwanted waste heat generation in the DC generator during periods when welding is not taking place, were not made.
Prior art relating to low cost alternator powered welding equipment has often opted for manual engine speed control to achieve proper power output for a given welding job. While low in cost, welding system efficiency and welding quality is typically poor when this approach is used. A number of factors combine to cause this. For example, alternator output power does not vary in a linear relationship with alternator rpm, and at the higher end of the alternator output curve, small variations in speed may produce rather large variations in output power. Since variations in output power demand, such as those caused by welding, increase or decrease the load placed on the engine by the alternator, and to a varying degree the engine speed, one can see that fine control of power becomes almost impossible. Additionally, alternator output power increases or decreases as internal temperatures increase or decrease. These temperature variations can occur as a result of welding, or as a result of simply generating welding energy. As these factors combine, constant compensating speed adjustments by the operator is required. To a large degree, power generation capability and utility, for a given mobile welding apparatus which uses an alternator to generate welding power without very sophisticated control mechanisms, is determined to a large degree by the physical size of the welding power generator itself and its ability to maintain relatively constant internal temperatures even while it is being operated at speeds which may provide very inefficient cooling, particularly when output power demand is high. This is a significant drawback in the case of retrofittable mobile welding systems, particularly in applications, where installation space is at a premium.
Prior art relating to alternator powered welding systems in which multiple weldors may simultaneously utilize a single engine as a power source to drive a plurality of independently controlled welding power generators is illustrated in U.S. Pat. No. 4,539,486. This patent proposes a solution in which a rather large, and expensive to produce, specially designed alternator is used in which a plurality of generator elements are combined and incorporated within a single welding power generator. Because magnetic and electrical interaction between the separate components of the generator cause undesirable effects during system operation, complicated electronic circuits are required to compensate for these effects. And, as with other prior art noted herein, constant current output is only attained by means of control circuitry requiring a means of electronic feedback. Further, in this invention, no means of combining and controlling the individual outputs of the individual generator elements in order to produce higher welding currents is possible.
In view of the foregoing problems, and as a weldor, and a designer of welders, the inventor has determined a complete gelding apparatus which can be driven by any suitable drive motor including but not limited to, internal combustion engines, hydraulic motors, pneumatic motors, or electric motors. This invention achieves very low manufacturing costs when compared to any prior art and includes features which allow it to be used effectively in commercial welding endeavors anywhere in the world, including areas in which no electrical power or technological support is available to a weldor/operator. The invention includes, in the embodiment described herein, a specially constructed alternator but it can also function acceptably using modified high-current automotive alternators. The invention also includes an electronic control mechanism which provides precise control of output power and voltage without the need for any expensive or complex feedback circuitry, and which enables the use of inexpensive remote operator controls which are, in the embodiment described herein, incorporated into a welding electrode holder. Operator controls may also be incorporated into any sort of remote control device suitable to the operator and the job to be performed (i.e., foot operated controls, a belt mounted control mechanism, other hand controls, infrared controls, etc.). These components work efficiently together to produce a welding energy unlike that of previous alternator-based welding devices with measurably superior welding performance characteristics. The invention""s wide range of potential control configurations make it easy to provide an operator with ergonomically designed user controls designed to greatly reduce weldor/operator workload as well as eliminating inadvertent shock and eye damage hazards for the weldor/operator in an absolute and essentially foolproof manner. In the embodiment of the invention specifically described herein, the operator controls include a welding output power control means so designed as to insure that no welding energy is present at the electrode holder, or in any part of the power generating and power transmitting means, at any time that welding is not actually taking place.
The invention produces a welding energy which can be transmitted over relatively long distances without the need to increase welding cable size and which offers greatly improved technical welding characteristics that enable a weldor to produce very high quality welds which show greater penetration into the workpiece for a given power setting than was previously possible while producing an easy to maintain arc even when a weldor places the welding electrode in direct contact with the weld puddle. Because of its ability to produce a stable arc deep within a weld puddle, the invention produces welds with less impurity within the weld joints which it produces than attainable with prior art.
Unlike prior art, the operation and control of the invention does not require precisely governed and/or regulated engine speed control.
The invention""s modular welding power generators can be operated and controlled independently, without undesirable electrical or magnetic interaction, when attached to, and powered by, a single drive motor. Further, the design of the invention""s independent modular welding power generator and its electronic control system, permits multiple welding power generators to be attached to a single drive motor with their outputs connected in parallel, while being controlled by a single electronic control mechanism, thereby enabling very high welding energy (i.e., from 300 to over 600 amps.) to be efficiently generated and precisely controlled at a very low manufacturing cost when compared with any previous technology.
This invention relates to a high frequency pulsed DC arc welding apparatus of a type which uses one, or more, electrically and mechanically inter-connectable and electronically controlled alternators, referred to herein as modular welding power generators, which are designed to be driven by a suitable drive motor. Said drive motors include, but are not limited to, internal combustion engines, hydraulic motors, pneumatic motors, or electric motors.
The welding power generators defined by this invention produce a welding energy suitable for use with all types of consumable electrodes (DC Stick and/or MIG) or non-consumable electrodes (TIG). These modular power generating units are electronically controlled and are so constructed as to be attached to or retrofittable to any type of drive motor (including engine driven vehicle such as tractors, automobiles, trucks, construction equipment, mowing equipment, nursery equipment, mining equipment, logging equipment, military equipment, and water-craft), or to be powered by any other type of suitable motor, including, but not limited to, internal combustion, electric, pneumatic, or hydraulically driven motors, which utilizes an ergonomically designed electrode holder incorporating a complete set of operator controls which are built into said electrode holder, which is capable of reliable operation in adverse environmental conditions, and which can produce an infinitely variable range of constant DC welding currents, at both standard and reverse polarities, without significant change in output (arc producing) voltage.
Invention features include:
1. a modular electronic control apparatus which includes in its design: an ergonomically configured welding electrode holder with welder operation controls built into the handle of the electrode holder, a control interface cable which is part of the welding cable assembly, and an electronic control module which is built into, or attached to, the invention""s alternator-based modular power generating device,
2. an air or fluid cooled alternator-based/power generating assembly designed to be motor driven and to operate continuously, at its maximum rated power, within a wide operating speed range defined to insure maximum effectiveness of its designed cooling system at all times when operating within this speed range, utilizing electronic controls rather than motor speed control to precisely, reliably, and inexpensively, control welder output current, without the need for electronic sensing and/or feedback of output current, and without the need for electronic or mechanical sensing and/or feedback of welding power generator or drive motor speed,
3. a solid-state electronic welding power control apparatus which provides a weldor with an infinitely, and instantaneously variable, range of well regulated output welding current settings without the need to vary drive motor speed or welding power generator speed, and without significant change in output (arc producing) voltage,
4. a solid-state electronic welding power control apparatus which provides a weldor with an infinitely, and instantaneously variable, range of well regulated output welding current settings and appropriate output (arc producing) voltages settings to insure proper welding arc function utilizing electronic controls rather than motor speed control to precisely and inexpensively, control welder output current, without the need to incorporate any mechanism for electronic sensing and/or feedback of output current, and without the need to incorporate any mechanism for electronic or mechanical sensing and/or feedback of welding power generator or drive motor speed,
5. a welding apparatus which is designed to operate outdoors in all climates including wet and/or otherwise adverse conditions,
6. a welding apparatus with inherent operator safety features, made possible by the invention""s electronic control system, which act positively and reliably to prevent inadvertent applications of welding energy which can cause injury to eyes, burns, or potentially lethal electrical shock to operators,
7. very compact, modular welding apparatus components which contribute significantly to the ease with which the invention can be installed into a given vehicle, or be attached to a given motor,
8. high (150 to over 800 amp.) continuous (100%) duty regulated welding current output,
9. a capability to replace existing vehicle electrical generating equipment in an emergency or when installation space is limited,
10. a capability for the power generating equipment and associated electronic controls to be utilized as a power source for TIG welding equipment, and
11. a low-parts count modular design which yields both high reliability and very low manufacturing costs,
12. a welding current generating system which incorporates a pulsating high frequency ripple component with a very well regulated constant DC welding current to produce a very stable and easy to maintain welding arc which produces good welding characteristics over a relatively wide range of arc lengths for a given electrode size (from 0 to over 2 times electrode diameter) and which provides significantly greater penetration, and produces significantly less weld joint impurities, when compared to a DC welding current without the pulsating high frequency ripple component.
Specifically, when comparing the invention to prior art, the invention greatly improves operator safety, significantly reduces weldor/operator work load, simplifies the welding process, simplifies product installation, offers all-weather utility, and dramatically improves weld quality over equivalent equipment at a significantly lower manufacturing cost than is possible with prior art known to the inventor.
Note that the complete scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
It is an object of the present invention to:
1. Provide an improved motor driven arc welding apparatus.
2. Provide a device which can easily be retrofitted to any existing vehicle engine, or to other suitable motors (including air and hydraulically driven motors), so as to use said engine/motor power to inductively generate appropriate welding currents.
3. Generate, by means of a specially constructed alternator, controlled by an electronic control means, and operated within a pre-defined speed range, a DC welding power output with a high frequency pulsating ripple component, in either standard or reversed polarity, which can be sustained without degradation, or equipment failure, in continuous use (100% duty cycle) situations.
4. Overcome all of the control and safety shortcomings in prior art, as noted previously herein.
5. Provide a weldor/operator with an unprecedented degree of real-time personal control over the complete welding process.
6. Provide a welding apparatus with an infinitely adjustable DC welding power source which (when used by an experienced weldor/operator) will significantly reduce weld impurities, increase weld penetration for a given power setting, and significantly improve weld appearance and quality when compared to prior art.
7. Provide a means to easily incorporate ergonomically designed operators controls, such as the electrode holder control system fully described in the embodiment of the invention which is described herein, which includes a complete set of welding apparatus controls, thereby significantly reducing operator workload and increasing weldor/operator safety.
8. Provide safety features which greatly reduce electrical shock hazards for the weldor/operator by insuring that no welding energy is produced unless appropriate conditions are met.
9. Provide a welding apparatus which can manufactured at a lower cost than any other welding device or apparatus which relies on prior art, without sacrificing the above identified performance features.
10. Utilize the same power generation source to weld with consumable stick-type electrodes, to weld with a wire feed type of consumable electrode (MIG) welding, or to provide a power source for non-consumable electrode (TIG) welding.
11. Generate precisely controlled welding current without the need for precise engine speed control or any sort of complicated power regulation circuitry which relies on mechanical or electrical feedback.
12. Allow multiple welding power generators, which are compact in size and inexpensive to produce when compared to large conventional motor-driven welding power generators, to be attached to a driving engine with their outputs connected in parallel while being controlled by a single electronic control mechanism, thereby enabling very high welding energy (i.e., from 300 to over 800 amps.) to be efficiently generated and precisely controlled at a very low cost when compared with any previous technology.
13. Allow more than one welding apparatus to be attached to the same engine and yet to be operated independently by multiple weldors.
The foregoing objectives have been achieved as will be seen in the detailed description of the invention which follows. Additional objects, features, and advantages of the invention will also become apparent.